An induction heat sealing device and a method for transversally seal a tube of packaging material

ABSTRACT

An induction heat sealing device ( 300 ) for providing a transversal sealing of a tube ( 104 ) of packaging material, said induction heat sealing device ( 300 ) comprising a main body ( 302 ) comprising a first and a second sealing surface ( 314   a,    314   b ) arranged to face the packaging material during a sealing state (S), a recess ( 308 ) provided in the main body ( 308 ) for receiving a knife during a cutting state (C), wherein the first and second sealing surface ( 314   a,    314   b ) are placed on opposite sides of the recess ( 308 ), and an electric conductor arrangement ( 306   a,    306   b,    306   c,    306   d ), provided in the main body ( 302 ), for inducing eddy currents in the packaging material during the sealing state (S), wherein at least part of the first and second sealing surface ( 314   a,    314   b ) are inclined and provided with a first and a second top section ( 316   a,    316   b ), respectively, such that particles in a product held inside the tube ( 104 ) are pushed away from a sealing band of the tube as the sealing band is pressed towards the first and second top section ( 316   a,    316   b ).

TECHNICAL FIELD

The invention generally relates to induction heat sealing. Moreparticularly, it is related to a device for providing transversalsealing of a tube of packaging material holding a liquid food product,and a method thereof.

BACKGROUND ART

Today it is well known to produce carton packages filled with liquidfood products, e.g. Tetra Brik™ packages filled with milk. The TetraBrik™ packaging machine is an example of a roll-fed packaging machine,sometimes also referred to as a roll-fed filling machine. In theroll-fed packaging machine a web of packaging material, provided to thepackaging machine on a reel, is formed into a tube and a longitudinalsealing is provided. After having formed the tube and provided thelongitudinal sealing, the tube is filled with product. From a lower endof the tube, transversal sealings are continuously made. In connectionwith making the transversal sealings, the lower end of the tube is cutoff such that packages filled with liquid product are formed. Thesepackages are thereafter transferred to a folding device that folds thepackages into their final form by making use of pre-made folding lines,sometimes also referred to as weakening lines, provided in the packagingmaterial.

Another type of packaging machine is so-called blanks-fed packagingmachines. Unlike the roll-fed packaging machine, the packages are madeone by one in the blanks-fed packaging machine. Another difference amongthe two is that the longitudinal sealing is not made in the packagingmachine, but is pre-made. A blank is thus in this context to be seen asa sleeve-shaped piece of packaging material. In the blanks-fed packagingmachine, the blank is erected, i.e. unfolded such that an inner space isformed. After being erected a closed end is formed by providing atransversal sealing in one end of the sleeve. In a next step product isfilled into the sleeve and thereafter another end of the sleeve isclosed by providing a transversal sealing such that a closed package isformed.

To make sure that the product is kept safely within the package, thetransversal sealings should be made in a reliable manner. Technology forproviding reliable transversal sealings has been used for many years,but since the requirements in terms of speed, e.g. number of packagesproduced per hour, different types of products to be filled into thepackages, e.g. high-viscous products and products containing seed andother types of particles, service intervals etc. are continuouslyincreasing, there is a need for improved transversal sealing technology.

SUMMARY

It is an object of the invention to at least partly overcome one or moreof the above-identified limitations of the prior art. In particular, itis an object to provide an improved induction heat sealing device.

According to a first aspect it is provided an induction heat sealingdevice for providing a transversal sealing of a tube of packagingmaterial, said induction heat sealing device comprising a main bodycomprising a first and a second sealing surface arranged to face thepackaging material during a sealing state, a recess provided in the mainbody for receiving a knife during a cutting state, wherein the first andsecond sealing surface are placed on opposite sides of the recess, andan electric conductor arrangement, provided in the main body, forinducing eddy currents in the packaging material during the sealingstate, wherein at least part of the first and second sealing surface areinclined and provided with a first and a second top section,respectively, such that particles in a product held inside the tube arepushed away from a sealing band of the tube as the first and second topsection are pressed towards the sealing band.

The induction heat sealing device may further comprise a magnetic fluxconcentrator arrangement holding the electric conductor arrangement,wherein the magnetic flux concentrator arrangement is provided with oneor several inclined magnetic flux concentrator top surfaces forming partof the first and second sealing surface.

The electronic conductor arrangement may be provided with one or severalinclined electronic conductor arrangement top surfaces forming part ofthe first and second sealing surface.

At least part of the first and second sealing surface may be inclinedsuch that a direction in which melted polymer in the packaging materialis moved as the induction heat sealing device (300) is pressed towardsthe sealing band is controlled.

An inclination profile of the first and second sealing surface of theheat sealing device (300) may be adapted for a specific type ofpackaging material having a specific type of polymer in the polymerlayer.

Further, an inclination profile of the first and second sealing surfaceof the heat sealing device may be adapted for a specific type of productcomprising a specific type of particles.

Additionally, an inclination profile of the first and second sealingsurface of the heat sealing device may be adapted for a specific type ofdynamics of a filling machine.

According to a second aspect it is provided a transversal sealing systemcomprising the induction heat sealing device according to the firstaspect, and a counter-pressure arrangement arranged opposite to theinduction heat sealing device, wherein the induction heat sealing deviceand the counter-pressure arrangement is arranged, in operation, suchthat the tube can be fed between the two.

The counter-pressure arrangement may comprise a first and a secondcounter-pressure element provided with a first and a second pressure padsurface, respectively, wherein the first and second counter-pressure padsurfaces are convex-shaped.

A first pressure pad top section of the first convex-shaped pressure padmay be offset the first top section of the first sealing surface of theinduction heat sealing device, and a second pressure pad top section ofthe second convex-shaped pressure pad may be offset the second topsection of the first sealing surface of the induction heat sealingdevice.

According to a third aspect it is provided a method for transversallyseal a tube of packaging material by using an induction heat sealingdevice comprising a main body comprising a first and a second sealingsurface arranged to face the packaging material during a sealing state,a recess provided in the main body for receiving a knife during acutting state, wherein the first and second sealing surface are placedon opposite sides of the recess, and an electric conductor arrangement,provided in the main body, for inducing eddy currents in the packagingmaterial during the sealing state, wherein at least part of the firstand second sealing surface are inclined and provided with a first and asecond top section, respectively, and a counter-pressure arrangementarranged opposite to the induction heat sealing device, said methodcomprising

-   -   placing the tube such that a sealing band of the tube is facing        the induction heat sealing device and the counter-pressure        arrangement,    -   moving the induction heat sealing device and the        counter-pressure arrangement towards one another such that        particles of the product held inside the tube is pushed away,    -   inducing eddy currents in the packaging material of the tube by        using the induction heat sealing device,    -   pressing a first side and a second side of the tube towards one        another such that the melted polymer in the polymer layer of the        first and the second side of the tube attach to each other, and    -   distributing the melted polymer using the inclined sealing        surfaces of the induction heat sealing device such that a risk        for insufficient sealing is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying schematic drawings, in which

FIG. 1 is a general illustration of a roll-fed packaging machine.

FIG. 2 is a more detailed view of a sealing apparatus used for providingtransversal sealings.

FIG. 3 illustrates a cross-sectional view of a heat induction sealingdevice.

FIG. 4 illustrates a transversal sealing system.

FIG. 5 illustrates a flow chart of a method for transversally seal atube of packaging material.

DETAILED DESCRIPTION

FIG. 1 generally illustrates a packaging machine 100. In the illustratedexample, the packaging machine 100 is a roll-fed carton packagingmachine. The general principle of such a machine is that from a roll ofpackaging material a web 102 is formed. Although not illustrated, ifneeded in order to fulfill food safety regulations, the web 102 may besterilized using a hydrogen peroxide bath, a Low Voltage Electron Beam(LVEB) device or any other apparatus capable of reducing a number ofunwanted microorganisms. After sterilization, by using a longitudinalsealing device, the web 102 can be formed into a tube 104. When havingformed the tube a product, for instance milk, can be fed into the tube104 via a product pipe 106 placed at least partly inside the tube 104.

In order to form a package 108 from the tube 104 filled with product, atransversal sealing can be made in a lower end of the tube by using asealing apparatus 110. Generally, the sealing apparatus 110 has two mainfunctions—providing the transversal sealing, i.e. welding two oppositesides of the tube together such that the product in a lower part of thetube, placed downward the sealing apparatus, is separated from theproduct in the tube placed upward the sealing apparatus, and cutting offthe lower part of the tube such that the package 108 is formed.Alternatively, instead of providing the transversal sealing and cuttingoff the lower part in one and the same apparatus as illustrated, thestep of cutting off the lower part may be made in a subsequent step by adifferent piece of equipment, or by the consumer if the packages areintended to be sold in a multi-pack.

In FIG. 2 a general principle of the sealing apparatus 110 isillustrated in further detail. The tube 104 can be fed from above sincethis provides for that product can be held inside the tube. In a firststage, a sealing stage S, a first jaw provided with a sealing device 200and a second jaw provided with a counter pressure device 202 are movedtowards each other such that two opposite sides of the tube 104 arepressed towards one another. In order to provide for the transversalsealing, heat can be provided by inducing eddy currents in the packagingmaterial while pressing the two opposite sides together. The heatprovides for that a polymer layer of the packaging material is melted,which in turn provides for the polymer layer can be used for making surethat the two opposite sides can attach to each other and stay togetherafter the jaws are removed. In a subsequent step, herein referred to asa cutting stage C, the lower part of the tube 104 can be cut off suchthat the package 108 is formed. In order to increase a speed in whichpackages are formed, the jaws can be moved together with the tube 104 ina tube feeding direction A during the sealing stage S and the cuttingstage C.

In order to provide for a more controlled forming process of the package108 so-called volume forming flaps 204 a, 204 b can be used. Morespecifically, by using these the tube 104 having a round cross-sectionmay be steered into a package 108 having a rectangular cross-section ina controlled manner.

The sealing device can be provided with two inductors, a first inductor206 a and a second inductor 206 b. In the illustrated example, the firstinductor 206 a is arranged above the second inductor 206 b. After havingprovided the transversal sealing a knife 208 can be used for cutting offthe lower part of the tube and thus form the package 108. In thisexample, the knife 208 and the first and second inductors 206 a, 206 bare provided in the sealing device, but other arrangements are alsopossible. For instance, the knife may be provided on the other side ofthe tube, in the counter pressure device, or the cutting step may beperformed by a separate device downstream the sealing device.

In FIG. 3 , by way of example, an induction heat sealing device 300 thatmay form part of the sealing apparatus 110 is illustrated in detail.More particularly, the induction heat sealing device 300 may be used asthe sealing device 200 illustrated in FIG. 2 .

The induction heat sealing device 300 can comprise a main body 302. Inthe main body 302 a magnetic flux concentrator arrangement 304 a-d maybe provided. A purpose of the magnetic flux concentrator arrangement 304a-d can be to direct the electromagnetic radiation formed by anelectronic conductor arrangement 306 a-d, that also can be comprised inthe main body 302, towards the tube 102 of packaging material during thesealing stage S. The magnetic flux concentrator arrangement 304 a-d canbe made of different materials, such as plasto-ferrite or soft magneticcomposite.

The induction heat sealing device 300 may be designed in different ways.In FIG. 3 , a so-called twin coil inductor is illustrated by way ofexample. In the twin coil inductor, the electronic conductor arrangement306 a-d may comprise a first coil 306 a-b and a second coil 306 c-d,that is, one coil is provided on either side of a recess 308 configuredto receive the knife during the cutting stage C. Another option, is aso-called single-coil inductor where one coil is provided and arrangedsuch that part of the coil is provided on one side of the recess 308 andanother part of the coil is provided on the other side of the recess308. Put differently, a first inductor 310 and a second inductor 312,representing a first part of the main body 302 on one side of the recess308 and a second part of the main body 302 on the other side of recess308, respectively, may share a single coil or may be provided with onecoil each, as illustrated in FIG. 3 .

Further, as illustrated, the electronic conductor arrangement 306 a-dmay be held by the magnetic flux concentrator arrangement 304 a-d suchthat the electronic conductor arrangement 306 a-d forms part of an outersurface of the main body 302. Another option, even though notillustrated, is that the electronic conductor arrangement 306 a-d isheld completely within the magnetic flux concentrator arrangement 304a-d such that the electronic conductor arrangement 306 a-d does not formpart of the outer surface of the main body 302. Still an option is tohave a surface cover, not illustrated, such that neither the magneticflux concentrator arrangement 304 a-d nor the electronic conductorarrangement 306 a-d form part of the outer surface.

A first and second sealing surface 314 a, 314 b of the first and secondinductor 310, 312, respectively, may be inclined as illustrated in FIG.3 . There are several advantages with having the first and secondsealing surfaces 314 a, 314 b inclined. First, during the sealing stageS, particles in the food product in the tube 104 may be pushed out froma sealing band of the tube 104, that is, a section of the tube 104 thatis to be formed into a transversal sealing, in a more controlled mannercompared to when having flat-surfaced inductors. More particularly, aneffect of having the first and second sealing surfaces 314 a, 314 binclined is that a pressure gradient can successively be built up insidethe tube 104. Since different products may differ in terms of e.g.viscosity and in that they comprise particles or not, and if comprisingparticles that these may have different properties, different productsmay require different measures for avoiding product residues in thesealing band. By customizing an inclination profile, that is how thesealing surfaces 314 a, 314 b are inclined, based on the product heldinside the tube 104, the pressure gradient build-up can be optimized forthe product, implying an even further improved transversal sealing.

In addition to improving that product residues are adequately removedfrom the sealing band in the sealing stage S, having the sealingsurfaces 314 a, 314 b inclined also has a positive effect on sealingquality. A pressure gradient is namely also formed in the polymer layerthat is melted during the sealing stage S. This provides for that howmelted polymer in the packaging material is moved can be controlled in amore precise manner compared to if using the flat-surfaced inductors. Inturn, this may result in that a risk of having aggregations of meltedpolymer in the packaging material can be reduced. Put differently, themelted polymer can be distributed more efficiently. Another positiveeffect is that less polymer may be required for making reliabletransversal sealing. Since how the melted polymer is distributed duringthe sealing stage S can be controlled in a more precise manner, this mayimply that less polymer is required, which is advantageous from anenvironmental point of view as well as from a cost perspective.

In the example illustrated in FIG. 3 , the first and second sealingsurface 314 a, 314 b are provided with a first and second top section316 a, 316 b, respectively. As illustrated, in this example the firstand second top section 316 a, 316 b are placed next to the recess 308,but other placements of the first and second top section 316 a, 316 bare also possible. Further, as illustrated in FIG. 3 , magnetic fluxconcentrator top surfaces 318 a-d can be inclined and form part of thefirst and second sealing surface 314 a, 314 b. As illustrated, alsoelectronic conductor arrangement top surfaces 320 a-d may be inclinedand form part of the sealing surface 314 a, 314 b. Further, the firstand second sealing surfaces 314 a, 314 b may be symmetrical with respectto a recess axis RA running through the recess 308.

FIG. 4 generally illustrates a transversal sealing system 400 comprisingthe induction heat sealing device 300 and a counter-pressure arrangement402 a, 402 b in turn comprising a first and a second counter-pressureelement 402 a, 402 b.

The induction heat sealing device 300 illustrated in FIG. 4 is differentfrom the one illustrated in FIG. 3 in that the first and second topsection 316 a, 316 b are placed in a mid-portion of the first and secondsealing surfaces 314 a, 314 b, respectively, instead of next to therecess 308 as is the case in the example illustrated in FIG. 3 .Further, the sealing surfaces 314 a, 314 b in the example illustrated inFIG. 4 is only inclined in part, that is, the sealing surfaces 314 a,314 b comprise inclined sections and flat sections.

The first and second counter-pressure element 402 a, 402 b may comprisea first and second counter pressure pad 404 a, 404 b, respectively,which may for instance be made of rubber or other elastic material. Thefirst and second counter pressure pad 404 a, 404 b can be provided witha first and a second counter-pressure pad surface 406 a, 406 b arrangedto face the tube 104 during the sealing stage S. The first and secondcounter-pressure pad surface 406 a, 406 b can be convex-shaped andprovided with a first and a second counter-pressure pad top section 408a, 408 b, respectively.

As illustrated in FIG. 4 , the first and second counter-pressure pad topsection 408 a, 408 b may be offset with respect to the first and secondtop section 316 a, 316 b, herein illustrated by a first pressure pad topsection FPPTS axis running through the first counter-pressure pad topsection 408 a, a second pressure pad top section SPPTS axis runningthrough the second counter-pressure pad top section 408 b, a first topsection FTS axis running through the first top section 316 a, and asecond top section STS axis running through the second top section 316b. Even though not illustrated, it is also possible to have the firstand second counter-pressure pad top section 408 a, 408 b aligned withrespect to the first and second top section 316 a, 316 b.

Further, as presented above, the inclination profile of the first andsecond sealing surface 314 a, 314 b may adjusted to meet needs of aspecific product, a specific packaging material, a specific type ofsealing apparatus 110, a specific packaging machine 100 or a combinationthereof. In addition, to even further improve sealing properties, alsoan inclination profile of the first and second counter-pressure padsurface 406 a, 406 b may be adjusted to meet the needs stated above.

In addition, the first and second counter-pressure element 402 a, 402 bmay be shaped differently such that the first and secondcounter-pressure pad surface 406 a, 406 b have different inclinationprofiles. One reason for having these shaped differently is that thetube 104, placed upstream the transversal sealing system 400, provides apressure caused by the food product held in the tube 104 down onto thetransversal sealing system 400. By having the first and secondcounter-pressure element 402 a, 402 b, and optionally also, or instead,the first and second inductor 310, 312 shaped differently, the pressurecaused by the food product can be compensated for.

FIG. 5 is a flow chart 500 illustrating a method for transversally sealthe tube 104 of packaging material by using the induction heat sealingdevice 300. The method can comprise placing 502 the tube 104 such thatthe sealing band of the tube is facing the induction heat sealing device300 and the counter-pressure arrangement 402 a, 402 b, moving 504 theinduction heat sealing device 300 and the counter-pressure arrangement402 a, 402 b towards one another such that particles of the product heldinside the tube is pushed away, inducing 506 eddy currents in thepackaging material of the tube by using the induction heat sealingdevice 300, pressing 508 the first side and the second side of the tube104 towards one another such that the melted polymer in the polymerlayer of the first and the second side of the tube attach to each other,and distributing 510 the melted polymer using the inclined sealingsurfaces of the induction heat sealing device 300 such that a risk forinsufficient sealing is reduced.

From the description above follows that, although various embodiments ofthe invention have been described and shown, the invention is notrestricted thereto, but may also be embodied in other ways within thescope of the subject-matter defined in the following claims.

1. An induction heat sealing device for providing a transversal sealingof a tube of packaging material, the induction heat sealing devicecomprising: a main body comprising a first sealing surface, a secondsealing surface, and a recess, the recess configured to receive a knife;and at least one electric conductor arrangement in the main body, the atleast one electric conductor arrangement configured to induce eddycurrents in the packaging material, wherein the first and second sealingsurface are on opposite sides of the recess, wherein the first sealingsurface has a first top portion adjacent to the recess, and wherein thesecond sealing surface has a second top section adjacent to the recess.2. The induction heat sealing device according to claim 1, wherein thefirst sealing surface and the second sealing surface slope downward awayfrom the recess
 3. The induction heat sealing device according to claim1, wherein the first sealing surface and the second sealing surface aresymmetrical with respect to the recess.
 4. An induction heat sealingdevice for providing a transversal sealing of a tube packaging material,the induction heat sealing device comprising: a main body comprising afirst sealing surface, a second sealing surface, and a recess, therecess configured to receive a knife; and at least one electricconductor arrangement in the main body, the at least one electricconductor arrangement configured to induce eddy currents in thepackaging material, wherein the first sealing surface and the secondsealing surface are on opposite sides of the recess, and wherein thefirst sealing surface comprises a first slope, a second slope comprisinga different slope angle from the first slope, and a first top portionbetween the first slope and the second slope.
 5. The induction heatsealing device according to claim 4, wherein the second sealing surfacecomprises a third slope, a fourth slope comprising a different slopeangle from the third slope, and a second top portion between the thirdslope and the fourth slope.
 6. The induction heat sealing deviceaccording to claim 4, wherein the first sealing surface and the secondsealing surface are symmetrical with respect to the recess.